Testing Native Language Neural Commitment at the Subcortical Level

Overview

This mentored student research project is funded by the Graduate Research Partnership Program with a projected timeline for data collection in the summer of 2015. Previous research has shown that language experience alters the way the human brain processes speech information. This phenomenon takes place very early in life and is referred to as Native Language Neural Commitment. For instance, as the Japanese language does not have the l-r speech sound contrast, Japanese infants start to show difficulty in hearing differences between the English l and r sounds at 12 months of age but not when they were at 6 months old. Learning the l-r distinction later in life proves to be very difficult for the Japanese school students and adults. Brain imaging studies have further revealed specific brain regions that are changed by language learning. But the evidence in support of the Native Language Neural Commitment theory is based on cortical-level measures. The proposed study extends the measurement to the subcortical level at the brainstem. The target language that the investigators are interested in studying is Mandarin Chinese, which is known for its use of lexical tones to express different words. For instance, the Chinese syllable "ma" means "mother" when it is spoken with a flat tone, and it means "hemp" when spoken with a rising tone. English, by contrast, does not employ lexical tones, and it is considered a non-tonal language. Does the Chinese learning experience fundamental change the way that pitch information is coded in the human brain? Does it happen at both cortical and subcortical levels? Previous research has shown evidence for a positive answer to both questions. But the direct evidence for brain-behavior correlations at the subcortical level is still missing. The proposed cross-language study will test Chinese-speaking and English-speaking adults to investigate Native Language Neural Commitment at the subcortical level. The investigators are interested in differences in the two subject populations by examining the relationship between brainstem pitch tracking and behavioral pitch perception in linguistic and nonlinguistic stimuli. The results of the proposed project will contribute to the understanding the role of the subcortical brainstem in Native Language Neural Commitment, which have significant implications for the development of auditory/speech training programs and assessment tools utilizing the brainstem frequency following measure to monitor progress in second language learning and test clinical populations.